1. Field
The invention relates to an intervertebral implant for mutual situating of adjacent vertebrae, enabling their displacement in sagittal and coronal plane, which can be applicable in the treatment of dysfunctions in all spinal segments, especially in the treatment of spondylolisthesis.
2. Discussion of the Prior Art
From the U.S. Pat. No. 5,888,228 an intervertebral implant is known, which is situated in the intervertebral body space and is designed for achieving the bone fusion, especially in the lumbar spinal segment. The implant is made in a form of a frame-type cage, opened on its top and base faces, it has got lateral surfaces, front wall and rear wall; there is a rotating element mounted in the cage. The outer surface of the rotating element is provided with a helical structure and protrudes beyond top and base face of the cage. The front wall and the rotating element have got an aperture for introduction of the drive tool, with which the rotating element fixed in the cage is rotated. The rotating element can be cylindrical or conical and can have holes. The offered solution acts as an interbody implant, and the rotating element located in the cage serves to introduce/screw the implant into the interbody space. This solution, however, doesn't give any opportunities to displace adjacent vertebrae relative to each other in the coronal or sagittal plane. From the patent application WO 2010/028056 an intervertebral implant is known for insertion into an intervertebral space between two adjacent vertebrae. The implant includes an intervertebral spacer and a spiral anchor coupling to the intervertebral spacer and two adjacent vertebral bodies. The spiral anchor is configured to partially embed within a portion of the vertebral body. The spiral anchor used in the implant fulfils the function of fixing of the implant to vertebrae. Presented solution is a usual intervertebral body cage, which keeps a distance between vertebrae after performed deposition of the intervertebral disc and allows for bone fusion.
From the patent application WO 01/66048 a two-part intervertebral implant is known, which is used for restoration of a spacing between adjacent vertebrae. The implant includes a spacer ring connected with a vertebra and a bore for introducing a locking element, which cooperates with a centre of the spacer's ring. The locking element has got a diameter or a height greater than the thickness of the spacer's ring and serves to lock the implant between two vertebrae. In one embodiment the spacer's ring can be C-shaped. In an alternative embodiment the spacer's ring can have a form of an intact ring having a side bore for receipt of the locking element.
The implant constitutes an intervertebral spacer with locking using the special element. The disadvantage of this solution is a lack of a possibility of displacement of vertebrae according each other by the implant.
From the patent application WO 00/16711 an interbody implant is known, for enhancing fusion of adjacent vertebrae. The implant comprises a form of rectangular cage member with an open construction, having a plurality of ribs for connection with plateaus of adjacent vertebral bodies. Ribs prevent the lateral shifting of the implant. The implant is held against the anterior/posterior motion by a locking screw, which engages the cage and adjacent bone tissue. The cage is adapted to be packed with a bone graft in order to improve bone fusion.
This solution is used to accelerate the bone fusion or to improve the possibility of arising of bone fusion and its aim is maintenance of the height of the intervertebral space, which was surgically restored. The disadvantage of this solution is lack of a possibility of mutual adjustment of vertebrae by the implant. A threaded element in a form of a screw is intended to blocking the implant in the intervertebral space, preventing displacement of the implant forward and backwards.
From the U.S. Pat. No. 6,210,442 is known implant for fusion of vertebral bodies, situated in the space between two adjacent vertebral bodies. The implant has got a supporting body, which opposite surfaces are situated between opposite vertebral bodies to achieve optimal fixation of the supporting body in the intervertebral space. The supporting body has got at least one location channel, which extends between supporting surfaces and is open on its top and bottom side. Into the location channel, there is introduced with rotational movement the fixing element provided with an external projection. The fixing element projects out of the open location channel. This solution is intended for fusing of vertebrae, serving simultaneously a function of an intervertebral spacer. Its construction doesn't allow for vertebral movement against each other.
From the patent application WO 9848738 is known implant for bone surgery comprising situated in the intervertebral space hollowed body with a pair of lateral walls enclosing and defining the intervertebral space and anchoring-reinforcement member, having on its outer surface anchoring projections with a diameter greater than body's overall height. The anchoring-reinforcement member is introduced into the inner space of the body with rotational movement. This solution ensures maintenance of the surgically restored intervertebral body space, serving as a distance-keeping element. It doesn't give, however, the possibility of displacement of vertebrae against each other.
From the patent application EP 1210920 is known a device for spinal fixation comprising main body, two-side pieces and fastening device for their symmetrical fastening with two sides of the main body. Two-side pieces are smaller in thickness than the main body. This solution allows for maintenance of restored during the surgery height of the intervertebral space and fixation leading to a bone fusion.
From the patent application US 2004/073214 is known an apparatus and a method for correction the spondylolisthesis. In this solution are used: a distractor of a discal space and separate correcting instrument for shifting the displaced vertebra into the proper position in a relation to the adjacent vertebra. The separate correcting instrument and the distractor of the discal space are used to perform initial stages of the correction, such as distraction of the discal space and incision of threads connecting with the stabilizing implant, and also for a correction of spondylolisthesis and maintenance of the correction before stabilization. This solution requires placement of an additional implant in the interbody space after the correction. The main disadvantage of this solution is the possibility of losing reposition during the act of changing of correction instrument for a stabilizing implant and increased number of tools required for performance both reposition and stabilization with the implant.
Presented above solutions mainly serve as distance-keeping elements, maintaining surgically restored height of the intervertebral space. The aim of rotational elements in a form of screws or anchors is to block implants between two vertebrae in their proper position, because their construction allows for dention into vertebral bodies. The majority of mentioned solutions don't assure, however, the possibility of displacement according to each other of adjacent vertebrae in a coronal or sagittal plane, especially in a treatment of spondylolisthesis. In turn in the solution US 2004/073214, which allows for mutual displacement of vertebrae, there is a possibility of losing of gained reposition and necessity of using additional implant to stabilize the correction.